They say a broken heart can kill you, but for one teenage girl and her little sister, falling in love really could prove fatal.

Chloe Church, 14, and her 11-year-old sister Evie have long known that an excessive shock could kill them because of their rare heart conditions. Yet growing up gives rise to a host of other problems – not least that doctors fear the emotional torment of a relationship could be deadly.

Chloe said: “I have had my first kiss and I survived. But I’ve never had the stress of a broken heart.”

The girls, from Swansea, suffer from Long QT syndrome, which means their hearts could stop pumping if they experience a rush of adrenaline

Parents Simon and Samantha make sure their daughters’ lives are as controlled as possible.

Chloe is not allowed to go to under-18s club nights with her friends and has to watch in envy as they take part in sports activities at school.

“If I dance too much or get too excited the adrenaline rush could kill me,” she said.

Mum Samantha, says she is constantly on edge, worrying about the effect that some activities will have on Chloe and her sister. The 43-year-old sales assistant said: “She’s frustrated we won’t let her go.”

The girls are not even allowed alarm clocks in case waking with a start causes a heart attack in one of them.